Manufacture of regenerated cellulose fibers



United States Patent "ice MANUFACTURE OF REGENERATED CELLU- LOSE FIBERS Werner Bandel, Kassel-Harleshausen, Germany, assignor to Spinnfaser Aktiengesellschaft, Kassel-Bettenliausen, Germany No Drawing. Filed Oct. 4, 1956, Ser. No. 613,826

Claims priority, application Germany Oct. 12, 1955 5 Claims. (Cl. 18-54) This invention in general relates to the production of synthetic fibers from viscose and more particularly to the production of crimped fibers having high crimping values.

For the atttainment of crimped fibers of viscose synthetic silk for use in fabrics in the cotton or woolen sector, processes heretofore have been developed based on the principle of spinning unripe viscose as, for example, viscose with a spinning ripeness of more than 12 H. Other means developed for heightening the degree of crimping involved increasing the alkali content of the viscose, the employment of spinning baths containing Zinc ion or spinning baths with a low sulfuric acid content and, finally, an increased stretching after removal from the first bath.

The application of the measures mentioned above cannot, however, as experiments have proved, be satisfactory in the production of threads with a high titre, such as those with a titre of 6 denier or more. For with the higher titre threads the desired crimping effect does not occur. The reduction of the sulfuric acid content in the spinning baths, furthermore, leads to sticking of the spun filament so that a perfect spinning is no longer assured.

Regenerated cellulose filaments may be manufactured by spinning viscose solutions in an acid bath. Broadly speaking, viscose solutions are solutions of alkali cellulose xanthate in dilute caustic soda. Alkali cellulose xanthate is prepared by first forming alkali cellulose by immersing cellulose in strong caustic soda solution. The alkali cellulose is then contacted with carbon disulfide to form the alkali cellulose xanthate which may be put in solution form by dissolving the composition in dilute alkali. The cellulose is regenerated when the carbon disulfide splits oif of the cellulose glucose side chain and the sodium cellulose is reduced to cellulose in an acid medium. In the usual viscose process the viscose solution is allowed to ripen to a point just before the alkali cellulose begins to precipitate or come out of solution. In the ripening period some of the cellulose xanthate decomposes into alkali cellulose and carbon disulfide. The alkali cellulose is held in the viscose solution as an emulsion by the remaining alkali cellulose xanthate. In the usual process, therefore, the remaining cellulose xanthate is decomposed in the first acid spinning bath. In the process of this invention the ripening, or decomposition, of the alkali cellulose xanthate does not proceed as far as in the usual viscose process. Thus, complete regeneration of cellulose from the incompletely ripened viscose occurs, not in the dilute acid solution used in spinning and stretching, but after the fibers in a lax state are contacted with additional dilute acid after the spinning and stretching operations.

It is an object of this invention to provide a process 2,966,391 Patented Dec. 27, 1960 for production of crimped fibers from viscose solutions, which process is equally applicable to high titre and low titre threads.

Another object of this invention is to provide a process for the manufacture of regenerated cellulose fibers with high crimping properties and high stretching and abrasion resistance values.

These objects can be achieved, especially in the production of coarse titred threads, by spinning unripe viscose having a ripeness not lower than 12 R, if the temperature of the spinning bath is maintained above C. and at the same time the sulfuric acid content of the bath is diminished in comparison to the concentration normally used. The concentration of sulfuric acid ranges between about and 125 grams per liter. Care is maintained, however, that the spinning bath has a high sodium sulfate content so that it has a specific gravity of at least 1.3 at 43 C. to prevent adherence of the individual filaments. In this manner, regenerated cellulose filaments are achieved, the filaments having very good fiber extension and very good abrasion resistance values, as well as high crimping properties. The high abrasion resistance values is especially important because the coarse titred fibers are extensively used in the production of carpets. The process is, however, not limited only to the production of coarse titred fibers.

The invention will be further understood from the following examples.

EXAMPLE I In the spinning of a 2.2 denier, highly crimped filament with a staple length of 40 millimeters, a viscose of the composition: cellulose, 8.6%; NaOH, 6.5%; and CS 37%, is spun at a ripeness of 19 H. in a spinning bath of the following compositions: 92-97 grams per liter sulfuric acid, 345-355 grams per liter sodium sulfate, and 10-l2 grams per liter of zinc sulfate. The spinning bath has a specific gravity at 43 C. of 1.305 to 1.31. The temperature of the bath is 70 C. The work is accomplished at a drawing off rate of 60 meters per minute, and after the removal from the first bath, stretching by 35% is done in a second bath which contains approximately 15-20 grams per liter sulfuric acid at a temperature of 95 C.

After the filaments are cut into the desired staple length they are immersed in another dilute acid bath at approximately 80 C. Here decomposition of the remaining cellulose xanthate is completed and the crimping of the filament occurs.

The improvement achieved by the processes of this in vention are readily apparent from the following tables which are a combination of data of fiber values for fibers spun in a spinning bath at 5 degree increments from 45 C. to 70 C.

Table I ORIMPING VALUES Uucrimp- Crimp- Temp., Arcs on ing Orimping Experiment C. mm. Resistning Cons- Fiber ance, Percent tancy,

mg. Percent Table II TEXTILE DATA Strength Stretching Crimp Experiment Temp., Titre Strength, Abras. Bending 0. Dry Value N 0.

Dry Wet Dry Wet 45 2. 07 23. 7 13. 7 17. 2 24. 1 7. 2 1, 050 2, 700 50 2. 11 23. 1 13. 9 16. 8 24. 6 6. 9 900 2, 800 55 2. 01 22. 9 14. 1 l8. 1 25. 8 7. 5 1,100 3, 010 60 2. 07 23. 4 14. 3 17. 8 27. 7. 3 1. 900 2. 900 65 2. 23. 9 14. 7 19. 7 29. S 7. 6 3. 200 3, 300 70 2. 1O 24. 3 15. 2 21. 1 31. 1 7. 4 4, 100 3, 100

EXAMPLE II result is transposed to a 100 millimeter length basis by In the manufacture of a 16 denier highly crimped regenerated cellulose filament with a staple length of 100 millimeters, a viscose of the composition: cellulose, 8.6%; NaOH, 6.5%; and CS 35.0% or 37.0%, is spun at a ripeness of 19 H. in a spinning bath of the following composition: 105-110 grams per liter sulfuric acid, 345- 355 grams per liter sodium sulfate, and -12 grams per liter zinc sulfate. The bath has a specific gravity at 43 C. of 1310-1320. The temperature of the bath is 70 C. The spun filaments are drawn off at a rate of 55 meters per minute and after removal from the spinning bath are stretched by 35-40% in a second bath which contains 20-30 grams per liter of sulfuric acid.

After the filaments thus produced are cut into the desired staple length, the residual cellulose Xanthate is split off in a hot acid bath and the fibers are further processed in the usual manner. The improvements of the processes of this invention in the manufacture of synthetic fibers for use in the manufacture of carpets will be readily apparent from the following tables wherein comparative fiber and textile data appear for fibers and textiles prepared by spinning at a varying first bath tempcrature.

Table III ORIMIPING VALUES multiplying 100 times the quotient of the number of arcs divided by the measured length of the crimped fiber.

The uncrimping resistance is the force in milligrams at which no further change occurs in the length of the fiber with additional loading. The amount of crimping, reported on a percentage basis, is determined by multiplying 100 times the quotient of the stretched length of the crimped fiber minus the the length of the crimped fiber in the unstretched state, the difference being divided by the length of the stretched fiber. The crimping constancy or stability is a measure of the recovery capacity in percent of the fiber crimping after a loading for 5 minutes with a weight equal to the uncrimping resistance plus an additional 50 milligrams. A measurement of the fiber length, taken one minute after removing the loading previously described, gives a value which may be used to calculate the recovery capacity of the fibers-the recovery capacity in percent being calculated by multiplying 100 times the quotient of the difference of the stretched length of the fiber minus the recovered length of the fiber after the five minutes loading previously described divided by the difference between the stretched length and the crimped length prior to any loading.

The abrasion values are determined on an apparatus consisting of an unglazed ceramic cylinder of 10 mm. diameter rotating at 80 r.p.m. The rotating cylinder is Arcs on Unmm Grim Grim continuously moistened with distilled water containing an Experiment; Temp, 100 mm ing ing ing 3. anionic sodium alkylnaphthalene sulfonate. The fiber is Q Fiber g r Percent ifg ggi in contact with the rotating cylinder over approxlmately one quarter of its circumference and is given a 1.5 fiberkilometer load during the test. The abrasion value is 48 66 250 19.1 49.3 55 70 255 20. 5 57.2 the number of revolutions of the cyhnder before the fiber 79 273 22. 1 55. 7 breaks 65 85 288 21.6 58.9 70 98 279 24.0 67.6 The bending number is the number of bends which the 50 fiber sustains at a 1.5 fiber-kilometer load under a bend- Table IV TEXTILE DATA Strength Stretching Crimp Bend- Experi- Temp, Titre Strength, Abrasion ing ment Dry Value No. Dry Wet Dry Wet The ripeness of the viscose solutions, reported in H. in the foregoing description, is determined by the Hottenroth test. In this test, 20 grams of the viscose to be tested are mixed with 30 ccs. of distilled water, and the solution is titrated with a 10% by weight ammonium chloride solution to bring about coagulation of the viscose to a gelatinous state. The ripeness value H.) is the number of ccs. of the ammonium chloride solution used to bring about the coagulation.

In the foregoing tables, the arcs on millimeters of fiber are determined by counting the number of arcs or bends in a measured length of the crimped fiber and the ing of 180 at a bending velocity of 300 double bends per minute. An apparatus which may be used for this test is that of the Knote Company of Leipzig, Germany.

The invention is hereby claimed as follows:

1. A process for manufacture from viscose of regenerated cellulose fibers with high crimping properties and high stretching and abrasion resistance values which comprises: spinning unripe viscose having a ripeness value of at least 14 H. in an acid spinning bath maintained at a temperature over 65 C. and being high in sodium sulfate content, the bath containing a small quantity of zinc sulfate and having a specific gravity of at least about 1.3 at 43 C.; stretching the filaments in a dilute acid bath; incompletely regenerating the cellulose in the spinning and stretching steps; and thereafter immersing the filaments in a lax state in dilute acid to complete the regeneration of the cellulose.

2. In a process for manufacture of regenerated cellulose fibers of high titre with high crimping values, the steps which comprise: spinning filaments of at least six denier from unripe viscose having a ripeness value of at least 12 H. in a dilute sulfuric acid spinning bath which contains a small quantity of zinc sulfate and is high in sodium sulfate content, said bath being maintained at a temperature over 65 C.; stretching said filaments; incompletely regenerating the cellulose in the spinning and stretching steps; cutting the filaments into the desired staple length; and immersing the resulting fibers in a lax state in a dilute acid bath to complete the regeneration of the cellulose.

3. In a process for manufacture of regenerated cellulose fibers of high titre with high crimping values, the steps which comprise: spinning filaments of at least six denier from unripe viscose having a ripeness value of at least 12 H. in a dilute sulfuric acid spinning bath Which contains a small quantity of zinc sulfate and is high in sodium sulfate content, said bath being maintained at a temperature over 65 C., the bath having a specific gravity of at least 1.3 at 43 C.; stretching said filaments; incompletely regenerating the cellulose in the spinning and stretching steps; cutting the filaments into the desired staple length; and immersing the resulting fibers in a lax state in a dilute acid bath to complete the regeneration of the cellulose.

4. In a process for the manufacture from viscose of regenerated cellulose filaments having high crimping, stretching and abrasion values, the steps which comprise: spinning unripe viscose having a ripeness value of at least 14 H. in a dilute sulfuric acid bath of 92 to 110 grams sulfuric acid per liter of water, said bath being maintained at a temperature over C., and said bath being high in sodium sulfate content, containing a small quantity of zinc sulfate and having a specific gravity of at least about 1.3 at 43 C. to avoid adherence of individual filaments; stretching the filaments in a second dilute sulfuric acid bath of 15 to 30 grams sulfuric acid per liter of water; incompletely regenerating the cellulose in the spinning and stretching steps; and thereafter immersing the filaments in a lax state in a dilute sulfuric acid bath suflicient to complete the regeneration of the cellulose.

5. In a process for the manufacture from viscose of regenerated cellulose filaments having a high filament titre and high crimping, stretching and abrasion values, the steps which comprise: spinning filaments of at least six denier from unripe viscose having a ripeness value of at least 14 H. in an aqueous bath containing to grams sulfuric acid per liter Water, 345 to 355 grams sodium sulfate per liter water, and 10 to 12 grams zinc sulfate per liter Water, said bath having a specific gravity at 43 C. of 1.31 to 1.32 and being maintained at a temperature about 70 C.; stretching the filaments by 35 to 40% in a second aqueous bath containing 20 to 30 grams sulfuric acid per liter water; incompletely regenerating the cellulose in the spinning and stretching steps; and thereafter immersing the filaments and a lax state in a dilute sulfuric acid bath sufficient to complete the regeneration of the cellulose.

References Cited in the file of this patent UNITED STATES PATENTS 2,301,003 Yetzsche Nov. 3, 1942 2,312,152 Davis Feb. 23, 1943 2,340,377 Graumann Feb. 1, 1944 2,440,057 Millhiser Apr. 20, 1948 2,696,423 Dietrich Dec. 7, 1954 2,852,333 Cox Sept. 16, 1958 

1. A PROCESS FOR MANUFACTURE FROM VISCOSE OF REGENERATED CELLULOSE FIBERS WITH HIGH CRIMPING PROPERTIES AND HIGH STRETCHING AND ABRASION RESISTANCE VALUES WHICH COMPRISES: SPINNING UNRIPE VISCOSE HAVING A RIPENESS VALUE OF AT LEAST 14*H. IN AN ACID SPINNING BATH MAINTAINED AT A TEMPERATURE OVER 65*C. AND BEING HIGH IN SODIUM SULFATE CONTENT, THE BATH CONTAINING A SMALL QUANTITY OF ZINC SULFATE AND HAVING A SPECIFIC GRAVITY OF AT LEAST ABOUT 1.3 AT 43*C., STRETCHING THE FILAMENTS IN A DILUTE ACID BATH, INCOMPLETELY REGENERATING THE CELLULOSE IN THE SPINNING AND STRETCHING STEPS, AND THEREAFTER IMMERSING THE FILAMENTS IN A LAX STATE IN DILUTE ACID TO COMPLETE THE REGENERATION OF THE CELLULOSE. 